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AA: arachidonic acid

AAADC: aromatic L-amino acid decarboxylase

α-BTX: α-bungarotoxin

AC: adenylyl cyclase

ACh: acetylcholine

AChE: acetylcholinesterase

AD: aldehyde dehydrogenase

ADH: alcohol dehydrogenase

anti-ChE: anti-cholinesterase

AP: action potential

AR: aldehyde reductase

AV: atrioventricular

CaM: calmodulin

CCK: cholecystokinin

CGRP: calcitonin gene–related peptide

ChAT: choline acetyl transferase

CHT1: Choline transporter

CNS: central nervous system

COMT: catechol-O-methyltransferase

CSF: cerebrospinal fluid

DA: dopamine

DAG: diacylglycerol

DAT: DA transporter

DβH: dopamine β-hydroxylase

DOMA: 3,4-dihydroxymandelic acid

DOPEG: 3,4-dihydroxyphenyl glycol

DOPGAL: dihydroxyphenylglycolaldehyde

ENS: enteric nervous system

ENT: extraneuronal transporter

EPI: epinephrine

EPP: end-plate potential

EPSP: excitatory postsynaptic potential

ET: endothelin

GABA: γ-aminobutyric acid

GI: gastrointestinal

GRK: G protein-coupled receptor kinase

GPCR: G protein–coupled receptor

HR: heart rate

5HT: serotonin (5-hydroxytryptamine)

HVA: homovanillic acid

IP3: inositol 1,4,5-trisphosphate

IPSP: inhibitory postsynaptic potential

KO: knockout

mAChR: muscarinic acetylcholine receptor

MAO: monoamine oxidase

MAPK: mitogen-activated protein kinase

mepps: miniature end-plate potentials

MOPEG: 3-methyl,4-hydroxyphenylglycol

MOPGAL: monohydroxyphenylglycolaldehyde

nAChR: nicotinic ACh receptor

NANC: nonadrenergic, noncholinergic

NE: norepinephrine (noradrenaline)

NET: norepinephrine transporter

NMJ: neuromuscular junction (of skeletal muscle)

NO: nitric oxide

NOS: nitric oxide synthase

NPY: neuropeptide Y

NSF: N-ethylmaleamide sensitive factor

PACAP: pituitary adenylyl cyclase–activating peptide

PG_: prostaglandin _, as in PGE2

PK_: protein kinase _, as in PKA

PL_: phospholipase _, as in PLA2, PLC, etc.

PNMT: phenylethanolamine-N-methyltransferase

PTX: pertussis toxin

rNTPase: releasable nucleotidase

SA: sinoatrial

SERT: serotonin transporter

SLC: solute carrier

SNAP: soluble NSF attachment protein, synaptosome-associated protein

SNARE: SNAP receptor

SST: somatostatin

STN: solitary tract nucleus

TH: tyrosine hydroxylase

VAChT: vesicular ACh transporter

VAT: vesicle-associated transporter

VIP: vasoactive intestinal polypeptide

VMA: vanillyl mandelic acid

VMAT2: vesicular uptake transporter


The autonomic nervous system, also called the visceral, vegetative, or involuntary nervous system, is distributed widely throughout the body and regulates autonomic functions that occur without conscious control. In the periphery, it consists of nerves, ganglia, and plexuses that innervate the heart, blood vessels, glands, other visceral organs, and smooth muscle in various tissues.

Differences Between Autonomic and Somatic Nerves

  • The efferent nerves of the autonomic nervous system supply all innervated structures of the body except skeletal muscle, which is served by somatic nerves.

  • The most distal synaptic junctions in the autonomic reflex arc occur in ganglia that are entirely outside the cerebrospinal axis. Somatic nerves contain no peripheral ganglia, and the synapses are located entirely within the cerebrospinal axis.

  • Many autonomic nerves form extensive peripheral plexuses; such networks are absent from the somatic system.

  • Postganglionic autonomic nerves generally are nonmyelinated; motor nerves to skeletal muscles are myelinated.

  • When the spinal efferent nerves are interrupted, smooth muscles and glands generally retain some level of spontaneous activity, whereas the denervated skeletal muscles are paralyzed.

Sensory Information: Afferent Fibers and Reflex Arcs

Afferent fibers from visceral structures are the first ...

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